This group would be classified as ‘vulnerable/impaired’ based on a framework of transport disadvantage developed by Currie et al. . They are particularly reliant on car travel and face high travel difficulties related to getting on and off buses, trains or trams, being able to get around alone, feeling safe when travelling, and experience an overall heightened risk of social exclusion due to transport disadvantage . Documented effects of lack of car transport include exclusion from accessing basic goods and services, social/recreational opportunities, and employment and education, with greater impacts identified in rural and remote areas . Lack of car access has also been identified as an important barrier to healthcare access, contributing to poorer chronic illness management and health outcomes. identified effects include an increase in missed appointments, delayed care, and poorer medication adherence, with one study quantifying an 88% increase in odds of ED presentation among individuals citing ‘lack of transport’ as a barrier to primary care use . For medicinal cannabis patients who do drive, when not impaired, they face the possibility of conviction under the presence offences and associated serious penalties including fines, licence suspensions or even imprisonment, a situation noted as problematic in a recent Australian Senate inquiry . However, they may also incur further substantial financial penalties if claiming compensation following a traffic-related accident and THC is detected in their blood or oral fluids. For example, in Victoria, patients who have THC detected in blood or oral fluids within 3 hours of driving following an accident, even if not at fault, can have their income compensation reduced by a third .

Driving restrictions have also been reported to be the major impediment to recruiting patients to medicinal cannabis clinical trials in Australia . Prohibiting driving for the length of a clinical trial, ebb and flow which can run for several weeks or months, is an onerous requirement that deters participants and results in reduced access to novel medicinal cannabis treatments.As international jurisdictions continue to move toward legalising and regulating access to cannabis, the issue of driving impairment and how to manage or deter such behaviour has gained greater attention. While some research has attempted to evaluate international approaches to deter driving under the influence of cannabis , there has been little attention given to how different jurisdictions have managed the legalisation of medicinal cannabis in relation to drug driving legislation. Although many jurisdictions have introduced medicinal cannabis access schemes over the last decade, some of these, such as Canada and most states within the United States, are far more permissive than Australia’s medical access model . Several of these overseas jurisdictions have also decriminalised or legalised the recreational use of cannabis and are therefore not comparable to Australia when considering road safety risks . An examination of regulatory and policy documents sourced primarily from governmental websites, identified several international jurisdictions which have introduced similar medical-only access models to Australia, with pharmaceutical grade products available only via prescription from a doctor. These jurisdictions include Norway, Ireland, the United Kingdom, Germany, and New Zealand. These countries, other than New Zealand, have drug driving presence offences relating to THC, similar to those that exist in Australia. However, in all cases they have adopted some form of medical defence enabling patients to drive when using a prescribed product as directed and not impaired .

In all countries listed, other than New Zealand, it remains an offence to drive if impaired. In many of these countries the medical defence applies to various prescription medicines that can be tested for and that have per se limits attached . However, in Ireland, where only illicit substances are tested for, a medical defence specific to medicinal cannabis was introduced and utilises a statutory medical exemption certificate . In Norway the medical exemption applies to registered medicines and health guidance recommends the patient not drive for 2 weeks after starting treatment . Other than medicinal cannabis, the only international example of a medical drug being included in zero-tolerance offences is benzodiazepines in Sweden, but patients there are not guilty of this offence if using the drug as directed by a doctor .As the number of patients accessing medicinal cannabis in Australia continues to increase, achieving the appropriate balance between road safety and patient access objectives is likely to gain further attention. Extensive experimental and epidemiological research indicates that the recreational use of cannabis is associated with a low to moderate increase in crash risk, which is of a similar or lower magnitude than several other potentially impairing prescription medications available and widely prescribed in Australia. However, the crash risk for prescribed medicinal cannabis is likely to be substantially lower due to a range of factors, with this outcome supported by available international epidemiological data that suggests a null road safety impact in jurisdictions introducing ‘medical only’ access models. Given this risk profile, the appropriateness of the current regulatory approach criminalising the presence of THC for medicinal cannabis patients irrespective of impairment is questionable.In all other jurisdictions, patients risk criminal conviction for the presence of THC, even when not impaired and using the medicine as directed by their doctor. This approach has serious negative impacts on patient access, health, and mobility.

It also fails to adhere to established principles that mobility should not be limited on the basis of a specific treatment, and that the potentially impairing effects of a medication should be balanced against a patient’s improvement in health and safe driving ability . These principles are incorporated into the risk minimisation framework used for other impairing prescription medications, coordinated via the TGA and state health and transport agencies. The discrepancy in the treatment of medicinal cannabis patients compared with patients using other impairing medications is particularly marked when considering that medical defences are currently in place for all other potentially impairing prescription medications that are included in drug driving presence offences in Australian jurisdictions . This creates a strange situation where medicinal cannabis patients are more vulnerable to prosecution than users of some illicit drugs who are able to drive while the drug is detectable in their bodily fluids if not impaired. Similarly, even recreational users of alcohol with a BAC 0.01 to 0.05, who have crash-risk odds of 1.2-1.8, face no restrictions on driving in normal circumstances . The question then arises whether there may be other specific issues relating to medicinal cannabis that necessitate a harsher approach for these patients. Some potential concerns include possible misuse or supplementation of medicinal cannabis with black market products, and the difficulty in communicating why medicinal cannabis patients can drive , but not recreational users. Both issues are common to, and currently managed for, other potentially impairing prescription medications, with the public now well-accustomed to different legal frameworks being in place for medical and illicit cannabis.But the value or justification for such an apparent higher evidence bar for medicinal cannabis is unclear, given the large number of observational and epidemiological studies that have already been undertaken in relation to THC, as well as agreement of recent meta-analyses of a relatively low risk profile even among recreational users . These studies provide an evidence base far exceeding numerous other known impairing medications.

It is also noteworthy that other countries with medicinal cannabis schemes similar to Australia’s tightly controlled, medical only access model, have implemented some form of exemption from usual drug driving offences for patients. In the UK, Norway, Germany, New Zealand and Ireland, patients with a valid prescription for medicinal cannabis who have taken the drug in accordance with instructions from a health practitioner are permitted to drive, as long as they are not impaired. While it is beyond the scope of this paper to examine the issue of how to define ‘impairment’ and the most effective means of establishing it at the roadside, standardised sobriety tests remain the most widely used method of screening for impairment internationally. They are also currently accepted by legal authorities in Australia as a valid screening tool for impairment caused by other potentially impairing prescription drugs, which are being prescribed at vastly higher rates than medicinal cannabis Although research assessing sensitivity and specificity to drugs aside from alcohol is limited and interactions with medical condition symptoms may complicate such assessments, sobriety tests have been found to be a moderate predictor of cannabis impairment . As such, we see little justification for not applying this method of detecting impairment to patients prescribed medicinal cannabis in Australia. There are also further policy options that may be considered alongside a medical defence or exemption for THC presence offences, including: requiring a zero blood alcohol limit for medicinal cannabis patients; prohibition from driving during the first weeks of treatment to allow for dose finding and tolerance development; specifying a maximum daily prescribed THC limit, above which the medical exemption would not apply; and simply improving patient education and advice. Due to the nature of THC metabolism and elimination, lack of correlation between oral fluid or blood levels and impairment in high frequency users, and the inability to provide accurate advice to patients regarding THC clearance, the use of oral fluid or blood threshold levels is near unworkable.

Even in Norway, for example, where an upper blood threshold of 9ng/ml has been adopted for the general population, an exemption from this limit is in place when medicinal cannabis has been prescribed by a doctor and is being used as directed . Ongoing improvement in roadside impairment detection, including the potential application of new technologies such as apps and artificial intelligence, is also important for improving enforcement of DUI/DWI offences and relevant for all potentially impairing medications, including medicinal cannabis. The current regulatory approach to medicinal cannabis and driving in most Australian jurisdictions, which criminalises the presence of THC in bodily fluids while driving irrespective of impairment, appears to derive from the historical status of cannabis as a Schedule 9 substance with no recognised medical value. There is little evidence to justify this differential treatment of medicinal cannabis patients, compared with those taking other potentially impairing medications. The relatively low risk profile of medicinal cannabis, dry racks harms associated with the current regulatory approach, and successful implementation of alternative policies in comparable countries suggest that a review of the regulatory framework for prescribed medicinal cannabis and driving in Australia is warranted. More broadly, our analysis suggests that in jurisdictions utilising doctor-supervised, medical-only access models, where medicinal cannabis is captured in broader medicines safety frameworks, patient exemptions from road safety THC ‘zero tolerance’ presence offences, as well as those based on per se limits, should be considered.Cannabis is commonly used for non-medical purposes throughout the world, where it remains illegal in most countries while undergoing legal status changes in selected others. In 2018, the prevalence of past-year cannabis use among 15-64 year-olds was estimated to be 3.8% , or about 200 million people who use cannabis globally .

Regional use is highest in North America, Oceania, and West Africa, with a past-year prevalence of 10-25%, followed by Europe and other regions. Moreover, and important for potential life-course outcomes, cannabis use is most common among adolescents and young adults . In this group, past-year prevalence is 25% or higher in high-use regions, often greater than tobacco use . An extensive body of literature documents the association of cannabis use with an increased risk for a variety of acute and long term health harms . These include: acute intoxication with impaired cognitive, memory and psychomotor skills; increased involvement in motor-vehicle crashes and related injury and deaths; impaired neurocognitive and psychosocial functioning; mental health problems ; cannabis use disorder/dependence; and select respiratory, reproductive, cardiovascular, gastro-intestinal conditions . Some of these associations are stronger than others, and causality is not always firmly established. reflecting the social epidemiology and specific vulnerabilities of this phenomenon, cannabis use-related problems are disproportionately concentrated in young adult males. However, the overall probabilities of cannabis-related harms need to be put into perspective. The vast majority of PWUC do not experience severe problems from their use, even with long-term exposure . The most serious problems arise in a sub-group of high-risk users, where up to half are estimated to develop cannabis use disorder.